Document pdrfork(2) and pdwait(2)

Reviewed by: asomers, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D54592

libsys: relocate implementations and manpages

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths

libsys: relocate implementations and manpages

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths to allow libc to find them in their new home.

Reviewed by: kib, emaste, imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/908

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Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

posix_spawn(3): handle potential signal issues with vfork

Described in [1], signal handlers running in a vfork child have
opportunities to corrupt the parent's state. Address this by adding a new
rf

posix_spawn(3): handle potential signal issues with vfork

Described in [1], signal handlers running in a vfork child have
opportunities to corrupt the parent's state. Address this by adding a new
rfork(2) flag, RFSPAWN, that has vfork(2) semantics but also resets signal
handlers in the child during creation.

x86 uses rfork_thread(3) instead of a direct rfork(2) because rfork with
RFMEM/RFSPAWN cannot work when the return address is stored on the stack --
further information about this problem is described under RFMEM in the
rfork(2) man page.

Addressing this has been identified as a prerequisite to using posix_spawn
in subprocess on FreeBSD [2].

[1] https://ewontfix.com/7/
[2] https://bugs.python.org/issue35823

Reviewed by: jilles, kib
Differential Revision: https://reviews.freebsd.org/D19058

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rfork(2): add RFSPAWN flag

When RFSPAWN is passed, rfork exhibits vfork(2) semantics but also resets
signal handlers in the child during creation to avoid a point of corruption
of parent state from

rfork(2): add RFSPAWN flag

When RFSPAWN is passed, rfork exhibits vfork(2) semantics but also resets
signal handlers in the child during creation to avoid a point of corruption
of parent state from the child.

This flag will be used by posix_spawn(3) to handle potential signal issues.

Reviewed by: jilles, kib
Differential Revision: https://reviews.freebsd.org/D19058

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Document RFTSIGZMB. Fix spelling of SIGCHLD. Note that signals are
delivered, not returned.

MFC after: 1 week

rfork(2): Discourage rfork_thread-like approaches.

Calling rfork_thread(3) does not interoperate with pthreads and global state
is not properly protected.

Remove the BUGS section suggesting LinuxTh

rfork(2): Discourage rfork_thread-like approaches.

Calling rfork_thread(3) does not interoperate with pthreads and global state
is not properly protected.

Remove the BUGS section suggesting LinuxThreads entirely. With the current
pthread library libthr, all threads are kernel-level entities so there seems
little reason to use LinuxThreads.

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Document RFTHREAD

PR: docs/78915
Submitted by: Marc Olzheim <marcolz@stack.nl>
MFC after: 1 week

Expand *n't contractions.

Sort sections.

Mechanically kill hard sentence breaks.

Correct the return value of vfork(2) and rfork(2) in their
manual page function prototypes.

mdoc(7) police: markup laundry.

Zap another reference to !RFPROC being unsupported that I missed before.

Don't use -compact in list of available flags. Fix tag width.

!RFPROC has been supported for a while now.

mdoc(7) police: "The .Fa argument.".

mdoc(7) police: Tidy up the syscall language.

Stop calling system calls "function calls".

Use "The .Fn system call" a-la "The .Nm utility".

When referring to a non-BSD implementation in
the HISTOR

mdoc(7) police: Tidy up the syscall language.

Stop calling system calls "function calls".

Use "The .Fn system call" a-la "The .Nm utility".

When referring to a non-BSD implementation in
the HISTORY section, call syscall a function,
to be safe.

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Update docs to reflect change in count of procs reserved for root
from 1 to 10.

PR: kern/40515
Submitted by: David Schultz <dschultz@uclink.Berkeley.EDU>
MFC after: 1 day

Document that rfork() will return EINVAL if flags not listed in the
manpage are passed in.

mdoc(7) police: Use the new .In macro for #include statements.

mdoc(7) police: join split punctuation to macro calls.

Remove whitespace at EOL.

Fix type-o

Submitted by: okazaki

mdoc(7) police: use canonical form of .Dd macro.